This invention relates generally to steering wheels and specifically to a steering wheel having a tapered hub sleeve therein.
In steering wheels for automotive vehicles, it is common to have a circular rim, a plurality of spokes and a central hub. The rim and spokes are usually encapsulated within a polymeric material. Traditionally, the rim is made from tubular steel. The hub is made from stamped steel and the spokes are stamped extension members or formed steel rods. The spokes are welded to the rim and the hub.
Furthermore, an annular hub sleeve is welded to the hub. The hub sleeve has a longitudinal bore with a plurality of longitudinally oriented broached splines therein. The sleeve serves to receive a mating steering shaft which is then longitudinally bolted to the hub. Typically, the inside surface surrounding the bore of the sleeve has a tapered portion and a substantially cylindrical portion. The cylindrical portion contains the splines. Moreover, the cylindrical portion is located closest to an inside face of the hub which faces the vehicle driver whereas the tapered portion is located furthest from the driver within the bore. Examples of such steering wheels are shown in the following U.S. Pat. No. 5,134,899 entitled "Steering Wheel Having Boss and Boss Plate Relative Rotation Prevention Means" which issued to Nagata et al. on Aug. 4, 1992; U.S. Pat. No. 5,090,731 entitled "Steering Wheel" which issued to Fujita et al. on Feb. 25, 1992; and, U.S. Pat. No. 4,738,157 entitled "Steering Wheel" which issued to Nishijima et al. on Apr. 19, 1988.
More recently, another steering wheel construction employs integrally cast spokes and a hub. The spokes merely encapsulate portions of a separate tubular rim. This version is disclosed in the following U.S. Pat. No. 5,085,097 entitled "Steering Wheel Core" which issued to Harata et al. on Feb. 4, 1992; U.S. Pat. No. 5,070,742 entitled "Steering Wheel" which issued to Sakane et al. on Dec. 10, 1991; and, U.S. Pat. No. 4,920,821 entitled "Steering Wheel for Vehicle" which issued to Shinto et al. on May 1, 1990. However, the hub sleeve is still a separately splined part that is inserted within or otherwise attached to the cast hub. The sleeve is commonly made from steel while the hub is usually made from a magnesium-based alloy. The sleeve is traditionally a separate part due to the conventional design and material limitations which have often proven inadequate to meet the various required strength standards. Other variations include a rim, spokes, and hub being integrally cast as a single unit. However, this steering wheel also has the aforementioned deficiencies.
A further cast steering wheel hub is known to have been manufactured and sold in Europe. In this steering wheel, a hub sleeve is integrally cast to the hub and shares a common casting material. This European sleeve has an inside surface defining a longitudinal bore comprised of a substantially constant hexagonally-shaped cross sectional portion located adjacent to an inside face of the hub closest to the vehicle driver and a hexagonally tapered cross sectional portion adjacent to an outside face of the hub.
The aforementioned separate hub sleeves are expensive to machine. They are also expensive to weld or insert within the hub. Furthermore, additional assembly labor and capital equipment are required to produce and attach these traditional sleeves.